Membrane adsorption has been introduced as an advanced method for protein purification. To achieve a high static binding capacity, often a ligand layer is attached by graft polymerisation to the internal surface of a microfiltration membrane. The binding sites are accessible by convective transport for a protein reducing internal transport resistance. In the work presented here, protein adsorption to ion-exchange membranes is investigated by a confocal microscope, which allows one to excite and detect fluorescence within a three-dimensional object with high local resolution. Proteins were labelled first with different fluorescent dyes, and observed by the confocal microscope after adsorption. The membrane structure itself can be visualised also by coupling of specific dyes. Thus, an image was created, which allows one to simultaneously 'see' the membrane and the protein bound to its pore structure. As a first evaluation of the high potential of this method, the adsorption of two model proteins, BSA and lysozyme, to a cation-exchange membrane was investigated. With an anionic exchange membrane formate dehydrogenase adsorption was studied.